Fluid operated tool having self-compensating throttle valve

ABSTRACT

A tool housing having a fluid supply passage leading to a fluid motor, a throttle valve received for movement in the passage between an open flow control position and a closed position, and a throttle control including a positively operated throttle actuator and a spring between the throttle valve and its actuator, the spring being preloaded upon operation of the actuator for effecting movement of the throttle valve independently of its actuator for automatically controlling fluid flow in the passage.

United States Patent [1 1 1 3,924,693

Whitehouse Dec. 9, 1975 FLUID OPERATED TOOL HAVING 2,661,765 12/1953Troy 251/80 x SELECQMPENSATING THROTTLE VALVE 2,740,507 4/1956 Shaff173/169 X 3,037,740 6/1962 Sheps et al.... 25l/285 X 5] Inventor: gWlntehnnse, Lyndhurst, 3,086,501 4/1963 Nielsen 251/285 x OhlO 3,373,8243/1968 whit/31161156 91/59 x [73] Assignee: The Stanley Works, NewBritain, FOREIGN PATENTS OR APPLICAT O S Conn- 1 372,325 3/1923 Germany173/169 [22] Filed: July 11, 1973 Primary Examinerlrwm C. Cohen PP N05378,154 Attorney, Agent, or FirmPrutzman, Hayes, Kalb &

Related US. Application Data Chllton [63] gsanntiirguxaettijon of Ser.No. 208,217, Dec. 15, 1971, ABSTRACT V A tool housing having a fluidsupply passage leading to [52] US. Cl. 173/169; 91/59; 91 /46g; a fluidmotor, a throttle valve received for movement 137/529 in the passagebetween an open flow control position [51] Int. Cl. B23B 45/04; F15B13/04 and a Closed position, and a throttle control luding [58] Field ofSearch 251/77, 28 5 322, 32 83; a positively operated throttle actuatorand a spring be- 91/59, 413, 468; 173/12 169; 137/529 tween the throttlevalve and its actuator, the spring being preloaded upon operation of theactuator for ef- [56] References Ci fecting movement of the throttlevalve independently UNTED STATES PATENTS of its actuator forautomatically controlling fluid flow in the passage. l,623,431 4/1927McVoy 137/529 1,681,044 8/1928 Malik 173/169 x Claims, 1 Drawing FigureI g dl 4 US. Patent Dec. 9, 1975 3,924,693

FLUID OPERATED TOOL HAVING SELF-COMPENSATING THROTTLE VALVE This is acontinuation of application Ser. No. 208,217, filed Dec. 15, 1971, andnow abandoned.

This invention generally relates to power tools and particularlyconcerns a fluid operated power tool having a so-calledself-compensating throttle valve.

A primary object of this invention is to provide a fluid operated toolhaving a new and improved self-compensating throttle valve which ispositively actuated by a manually operable trigger and which thenautomatically varies fluid flow to afluid motor responsive to change inthe operating speed of the tool to effect a controlled torque outputwhile the trigger remains fully actuated.

Another object of this invention is to provide a selfcompensatingthrottle valve of the type described which is quick and easy tomanufacture and install on a fluid operated tool and which is readilyadjustable for desired tool performance over a broad range of operatingrequirements.

A further object of this invention is to provide a new and improvedself-compensating throttle valve for use with fluid operated tools andwhich is of simplified but rugged construction for reliable service overan extended period of time.

Other objects will be in part obvious and in part pointed out in moredetail hereinafter.

A better understanding of the objects, advantages, features, propertiesand relationships of the invention will be obtained from the followingdetailed description and accompanying drawing which set forth anillustrative embodiment indicative of the way in which the principle ofthis invention is employed.

The drawing shows a fragmentary view, partly in section and partlybroken away, of a fluid operated power tool incorporating a preferredembodiment of this invention.

Referring to the drawing in detail, a fluid operated power tool such asa pneumatic drill is shown for illustrative purposes, although it is tobe understood that this invention may be used in a variety of differenttypes of fluid operated power tools. The drill 10 has a housing 12 witha contoured depending pistol grip l4, and a fluid motor, such as aconventional rotary vane type air motor 16, is mounted in the housing 12for driving a work engaging element of the tool, not shown. Compressedair for driving the motor 16 is supplied through a coupling, not shown,at the bottom of the pisto] grip 14 and flows through a passage 18comprising a series of passageways, leading to the air motor 16.

An inlet supply line 20 and a motor outlet line 30 (depicted by brokenlines) of the passage 18 are interconnected through a valve chamber 24,defined by a cylindrical valve body 26 suitably secured in a bore 28extending across the housing 12. The valve bore 28 has a multiplediameter inner end providing a pair of coaxial compartments 32 and 34which connect the valve chamber 24 with the supply line 20. Compartment32 is of an intermediate size relative to the full diameter portion ofthe valve bore 28 and its reduced terminal compartment 34, and aconcentric annular shoulder 36 is formed in the housing 12 at thejuncture of the intermediate compartment 32 with the full diameterportion of the valve bore 28.

The elongated axially extending valve chamber 24 of the valve body 26terminates in a concentric compartment 38 of enlarged diameter within acupshaped inner end of the valve body 26. An O ring seal 40 is disposedbetween a shoulder 42 adjacent the inner end of the valve body 26 andshoulder 36 of the housing 12 to prevent undesired air leakage past thevalve body 26 and the surrounding portions of the housing 12. The valvechamber 24 is accordingly suited to serve as a part of the fluid supplypassage 18 to communicate its inlet supply line 20 with the motor outletline 30 via a port shown in broken lines at 44 which will be understoodto extend radially outwardly through the valve body 26 to interconnectits valve chamber 24 with the motor outlet line 30.

For controlling air flow through the passage 18, a valve member 46 isprovided on a throttle valve 48 reciprocably mounted within the chamber24. In the specifically illustrated embodiment, the valve member 46 isprovided by an O ring seal disposed within an annular groove 50 on arearwardly extending coaxial stem 52 of the throttle valve 48. The mainbody of the valve 48 is enlarged relative to its stem 52 which isprovided with an annular flange 54 on one side of which is formed thegroove 50 on the stem 52, within which the O ring seal is mounted, andthe other side of which seats a valve closure compression spring 56. Thespring 56 is biased between the flange 54 and a housing portion definingan end wall 58 for the bore 28 to hold the throttle valve 48 in itsillustrated normally closed position with the valve body surrounding theinner end of the chamber 24 and providing a valve seat for member 46.

The throttle valve 48 is shown having its full diameter main bodysuitably contoured with a symetrically fluted construction to permitfluid flow past the valve 48 within its chamber 24 responsive to itsbeing moved in a valve opening direction from left to right as viewed inthe drawing. The inner end of the main valve body is tapered as at 60from its juncture with the stem 52 in a direction away from the valvemember 46 to provide a graduated reduced intermediate portion formetering inlet airflow to the motor 16 upon opening the throttle valve48.

For positively actuating the throttle valve, a manually operable trigger62 is shown suitably secured, e.g., by a roll pin 64, to an actuatingshaft 66 axially extending into the valve chamber 24 and having anintegral concentric throttle pin 68 of reduced diameter extendingrearwardly of the shaft 66 for positively actuating the throttle valve48. The actuating shaft 66 has an intermediate portion of reduced sizeforming a longitudinally extending notch 70 through which is extended asecond roll pin 72 to retain the shaft 66 and its trigger 62 in assemblywith the valve body 26 while yet permitting limited freedom oflongitudinal reciprocating movement of the actuating shaft 66 within thevalve chamber 24. In its illustrated normal rest position, the throttlepin 68 of the actuating shaft 66 is spaced apart a preselected distancefrom the throttle valve 48 in its normally closed position.

From the foregoing description, it will be seen that upon squeezing thetrigger 62, the actuating shaft 66 will be depressed rearwardly into thevalve chamber 24, from left to right, as viewed in the drawing, and itsintegral throttle pin 68 will positively engage the throttle valve 48 tounseat its valve member 46 and permit air to flow through the passage 18to actuate the motor 16.

To preselect a desired motor operating speed under free runningconditions, an adjustment nut 74 isthreadably mounted on an externallythreaded, forwardly projecting, reduced end portion 76 on the valve body26. The nut 74 has a forward abutment stop face 78 for engagement withsurface 80 of the trigger 62. Accordingly, the abutment stop surface 78may be axially adjusted relative to the valve body 26, and thus to thetrigger 62 and its actuating shaft 66, by simply rotating a knurledshoulder 84 of the adjustment nut 74 such that the maximum rearwardtrigger displacement from its normal rest position may be selectivelylimited to a desired throttle valve opening upon initial actuation ofthe air motor and, accordingly, set its speed of operation during idlingunder no load conditions.

To maintain the adjustment nut 74 in a selected position, an annularseries of detent recesses such as at 86 will be understood to be formedaround the inside wall of the adjustment nut 74 confronting the valvebody 26. A detent pin 88 is received in an opening 90 formed in a lowerportion of valve body 26 and a suitable spring 92 is fitted within theopening 90 to urge the detent pin 88 axially outwardly for registrationwith the annular series of detent recesses 86 and to maintain theadjustment nut 74 in a selected angular position. The angular positionof the adjustment nut 74 relative to the valve body 26 is readilyestablished by an operator for a desired idling speed by suitableindicia 94 marked on the adjustment nut 74, it being understood that theindicia 94 is calibrated to different motor idling speeds as determinedby the extent of the throttle valve opening displacement for a given airsupply pressure and a given size air motor.

With a conventional throttle valve having a solid integral shaftconnected to the trigger, as normally associates with such power tools,a change in throttle valve opening displacement would not only changethe idling speed but also the available torque. To maintain torquecharacteristics at slower idling speeds, the valve must open further inresponse to torque loading. A force is available for this in that as anair motor is loaded, its speed decreases, its airflow demand decreases,and its operating pressure downstream of the restricting speedcontrolling throttle valve rises.

As noted above, upon squeezing the trigger 62, the throttle pin 68positively engages the throttle valve to unseat the valve member 46 andmove it to an open flow control position as established by the extent ofactuator movement permitted by the adjustment nut 74 to allow air flowthrough the passage 18 to the motor under idle or free runningconditions. Actuation of the throttle valve 48, however, simultaneouslycompresses a compensating spring 96 located in valve chamber 24 betweenactuating shaft 66 and throttle valve 48. As the tool is loaded and themotor operating speed decreases, the preloaded resilient force of thecompressed compensating spring 96, together with the increaseddownstream motor operating pressure within the valve chamber 24, jointlyact upon the throttle valve 48 to move it further in a valve openingdirection from left to right, as viewed in the drawing, against theopposing upstream line pressure and biasing force of the valve closurespring 56 to automatically provide increased air flow through the valvechamber 24 past the throttle valve 48 to increase the motor operatingspeed and the output force of the motor 16 during increased loading ofthe tool 10.

Upon trigger release, the bias effected by the compensation spring 96 isalso released, and the biasing force of the valve closure spring 56 issufficient to overcome the motor operating pressure in the valve chamber24 and to close the valve member 46 into sealing engagement with itsvalve seat and through the compensating spring 96, to return theactuating shaft 66 and operating trigger 62 to their illustrated normalrest position.

It will be seen that the self-compensating throttle valve 48 of thisinvention effects a controlled fluid flow to the motor 16 responsive tothe torque loading on the tool 10 as reflected by changes in motoroperating speed, due to the combination of opposed spring forces and theopposed pneumatic forces on the throttle valve 48 to provide for openingit further as the downstream motor operating pressure increases, evenwhen the trigger 62 is squeezed and retained in a fully retracted,actuated position.

The above described self-compensating throttle valve is particularlyuseful with grinders, various fastener tools and similar tools such asthe illustrated pneumatic drill. For example, in the use of thepneumatic drill, a proper speed may be selected for the material of theworkpeice and the type and diameter drill bit which is to be used. Thefeed in hand drilling, e.g., is accomplished by arm thrust against thetool. A drill incorporating the disclosed self-compensating throttlevalve will normally drill holes easily in a variety of materials withnormal arm thrust without burning or snapping the drill bits and withoutglazing or hardening the workpiece while ensuring that full torque isavailable at the time the drill bit breaks through the workpiece. Thedisclosed construction is simplified but rugged and easily manufacturedand assembled while at the same time providing reliable performance overan extended period of time with minimum service requirements.

As will be apparent to persons skilled in the art, variousmodifications, adaptations and variations of the foregoing specificdisclosure can be made without departing from the teachings of thepresent invention.

I claim:

1. In a power tool having a pneumatically operated drive motor, acontrol valve having a fluid inlet adapted to be connected to apneumatic pressure source and a fluid outlet connected to the drivemotor, a valve bore interconnecting the valve inlet and valve outletproviding a fluid passageway therebetween, a valve seat surrounding thebore intermediate the valve bore inlet and outlet, a valve membermounted in the bore shiftable in first and second opposite axialdirections therein respectively to and from a respective closed positionthereof for selectively seating on said valve seat and closing saidfluid passageway and providing a variable and decreasing fluidrestriction between the valve inlet and outlet as the valve member isshifted in said second opening direction from its closed position, thevalve member being mounted to be biased in the first closing directionby the valve inlet pressure and in the second opening direction by thevalve outlet pressure, the valve member being mounted in the bore suchthat the net fluid pressure force on the valve member is in said firstclosing direction and is a function of the pressure drop from the valveinlet to the valve outlet and therefore the fluid restrictiontherebetween, first spring means biasing the valve member in saidclosing direction and manually operated valve control means forselectively-shifting the valve in said opening direction for controllingthe pneumatic operation of the drive motor, the improvement wherein themanually operated valve control means comprises second spring meansbiasing the valve member in the opening direction and manual actuatormeans for manually actuating the valve member in said opening directionfrom its closed position, said manual actuator means closing the bore atan end thereof and continuously sealing the bore from atmosphere, saidsecond spring means being mounted between said valve member and saidmanual actuator means, said manual actuator means manually selectivelyvarying the opening spring bias on the valve member in excess of theopposing closing spring bias on the valve member such that the openaxial position of the valve member is dependent on the relative openingand closing spring bias on the valve member and on the pressure drop andtherefore the fluid restriction between the valve inlet and valve outletand the valve member automatically compensates for drive motor speed andtherefore drive motor load for varying the valve opening in accordancewith the drive motor load.

2. A power tool according to claim 1 wherein the second spring means isa compression spring.

3. A power tool according to claim 1 wherein the manual actuator meansis selectively operable from a first position to a second position forengaging and initially shifting the valve member in said openingdirection from its closed position, and wherein the second spring means,with the actuator means in its second position, has sufficient bias toshift the valve member further in said opening direction so that thevalve member thereupon automatically compensates for drive motor speed.

1. In a power tool having a pneumatically operated drive motor, acontrol valve having a fluid inlet adapted to be connected to apneumatic pressure source and a fluid outlet connected to the drivemotor, a valve bore interconnecting the valve inlet and valve outletproviding a fluid passageway therebetween, a valve seat surrounding thebore intermediate the valve bore inlet and outlet, a valve membermounted in the bore shiftable in first and second opposite axialdirections therein respectively to and from a respective closed positionthereof for selectively seating on said valve seat and closing saidfluid passageway and providing a variable and decreasing fluidrestriction between the valve inlet and outlet as the valve member isshifted in said second opening direction from its closed position, thevalve member being mounted to be biased in the first closing directionby the valve inlet pressure and in the second opening direction by thevalve outlet pressure, the valve member being mounted in the bore suchthat the net fluid pressure force on the valve member is in said firstclosing direction and is a function of the pressure drop from the valveinlet to the valve outlet and therefore the fluid restrictiontherebetween, first spring means biasing the valve member in saidclosing direction and manually operated valve control means forselectively shifting the valve in said opening direction for controllingthe pneumatic operation of the drive motor, the improvement wherein themanually operated valve control means comprises second spring meansbiasing the valve member in the opening direction and manual actuatormeans for manually actuating the valve member in said opening directionfrom its closed position, said manual actuator means closing the bore atan end thereof and continuously sealing the bore from atmosphere, saidsecond spring means being mounted between said valve member and saidmanual actuator means, said manual actuator means manually selectivelyvarying the opening spring bias on the valve member in excess of theopposing closing spring bias on the valve member such that the openaxial position of the valve member is dependent on the relative openingand closing spring bias on the valve member and on the pressure drop andthErefore the fluid restriction between the valve inlet and valve outletand the valve member automatically compensates for drive motor speed andtherefore drive motor load for varying the valve opening in accordancewith the drive motor load.
 2. A power tool according to claim 1 whereinthe second spring means is a compression spring.
 3. A power toolaccording to claim 1 wherein the manual actuator means is selectivelyoperable from a first position to a second position for engaging andinitially shifting the valve member in said opening direction from itsclosed position, and wherein the second spring means, with the actuatormeans in its second position, has sufficient bias to shift the valvemember further in said opening direction so that the valve memberthereupon automatically compensates for drive motor speed.